I. Field
This disclosure is related to antennas. More particularly, this disclosure is related to ferrite loaded loop antennas.
II. Background
It is understood in the art that electrically small antennas, such as the loop antenna are inherently inefficient. However, due to their reduced size, antenna designers have expended a significant amount of effort in studying the loop antenna. A loop antenna can be formed from a wire shaped in the form of a loop. From Faraday's law, magnetic fields that “cut” through the plane of the loop will induce a voltage in the loop, thus enabling the loop to act as a receiving antenna. If a current is forced into one end of the loop, then electromagnetic fields from the current will radiate from the plane of the loop and the loop can be operated as a transmitting antenna.
Practitioners, having recognized the reduced size of a loop antenna as compared to a dipole or monopole antenna, have attempted to increase the sensitivity or gain of the loop antenna by replacing the air core of the loop antenna with a ferrite core. The ferrite core aids in concentrating magnetic fields through the loop rather than outside the loop, thus increasing the voltage in the loop antenna. However, the addition of ferrite to increase the magnetic flux in the loop has drawbacks. In the transmit mode, due to heating effects of the ferrite core, the transmitting capabilities of the loop antenna is significantly compromised. Thus, the use of ferrite loaded antennas have not progressed much more beyond anything other than as a receive antenna.
In this disclosure, a ferrite loaded loop antenna is configured in such a manner that the transmit capabilities and frequency response capabilities are enhanced while still preserving general broadband characteristics.